<style>
    .mapboxgl-popup {
        max-width: 400px;
        font: 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
    }
</style>
<div id="map"></div>
<script>
    var map = new mapboxgl.Map({
        container: 'map',
        style: 'mapbox://styles/mapbox/streets-v11',
        center: [-100.04, 38.907],
        zoom: 3
    });

    map.on('load', function() {
        // Add a source for the state polygons.
        map.addSource('states', {
            'type': 'geojson',
            'data':
                'https://d2ad6b4ur7yvpq.cloudfront.net/naturalearth-3.3.0/ne_110m_admin_1_states_provinces_shp.geojson'
        });

        // Add a layer showing the state polygons.
        map.addLayer({
            'id': 'states-layer',
            'type': 'fill',
            'source': 'states',
            'paint': {
                'fill-color': 'rgba(200, 100, 240, 0.4)',
                'fill-outline-color': 'rgba(200, 100, 240, 1)'
            }
        });

        // When a click event occurs on a feature in the states layer, open a popup at the
        // location of the click, with description HTML from its properties.
        map.on('click', 'states-layer', function(e) {
            new mapboxgl.Popup()
                .setLngLat(e.lngLat)
                .setHTML(e.features[0].properties.name)
                .addTo(map);
        });

        // Change the cursor to a pointer when the mouse is over the states layer.
        map.on('mouseenter', 'states-layer', function() {
            map.getCanvas().style.cursor = 'pointer';
        });

        // Change it back to a pointer when it leaves.
        map.on('mouseleave', 'states-layer', function() {
            map.getCanvas().style.cursor = '';
        });
    });
</script>
